1. Field of Invention
The present invention relates to fuser or fixing members, and processes for making such fuser and fixing members. In particular, the present invention relates to processes for making such fuser and fixing members, or other members, where curing of applied layers is conducted using infrared or other radiant heat sources. The present invention also relates to developing apparatuses using such fusing and fixing members.
2. Description of Related Art
In a typical electrostatographic printing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be a photosensitive member itself or other support sheet such as plain paper, transparency, specialty coated paper, or the like.
The use of thermal energy for fixing toner images onto a support member is well known. In order to fuse electroscopic toner material onto a support surface permanently by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90xc2x0 C. to about 160xc2x0 C. or higher, depending upon the softening range of the particular resin used in the toner. It is not desirable, however, to raise the temperature of the substrate substantially higher than about 200xc2x0 C. because of the tendency of the substrate to discolor at such elevated temperatures particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means, including a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles generally takes place when the proper combination of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines, process conditions, and printing substrates.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate and/or belt members. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus, increasing the background or interfering with the material being copied there. The so called xe2x80x9chot offsetxe2x80x9d occurs when the temperature of the toner is raised to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member.
The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface that has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser members to ensure that the toner is completely released from the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset. In addition to preventing hot offset, it is desirable to provide an operational latitude as large as possible. By operational latitude it is intended to mean the difference in temperature between the minimum temperature required to fix the toner to the paper, the minimum fix temperature, and the temperature at which the hot toner will offset to the fuser roll, the hot offset temperature.
Generally, fuser and fixing rolls are prepared by applying one or more layers to a suitable substrate. For example, cylindrical fuser and fixer rolls are typically prepared by applying a fluoroelastomer layer, with or without additional layers, to an aluminum core. The coated roll is then heated in a convection oven to cure the fluoroelastomer material. Such processing is disclosed in, for example, U.S. Pat. Nos. 5,501,881, 5,512,409 and 5,729,813, the entire disclosures of which are incorporated herein by reference.
A problem with conventional processing, however, is that the convection oven curing of the fuser or similar members requires lengthy processing time, which typically exceeds about 16, 28, 20 or more hours. For example, U.S. Pat. No. 5,759,813 discloses that the coating is cured by a stepwise heating process totaling about 24 hours, such as 2 hours at 95xc2x0 C., 2 hours at 150xc2x0 C., 2 hours at 175xc2x0 C., 2 hours at 200xc2x0 C. and 16 hours at 230xc2x0 C., followed by cooling and sanding. Such lengthy curing processes, in addition to being time-consuming, are energy intensive and often require batch, rather than continuous, process operation.
Furthermore, a problem experienced with such convection oven curing of the fuser or fixing members is that the convection curing process can be detrimental in cases where the cure temperature of the coating is higher than the process temperature of the substrate and/or subsequent coatings. In these cases, the high temperatures needed to cure the fluoroelastomer coating can cause undesired changes in the substrate or other layers, altering the layers"" chemical compositions and/or properties.
There is a need in the art for improved coating and curing processes, whereby the above disadvantages of the prior art convection curing processes can be overcome. Likewise, there is a need in the art for a curing process that has a higher throughput rate while still providing economic and materials advantages in forming fusing members, fixing members, and the like. These and other advantages are provided by the present invention.
The present invention provides fuser and fixing members, and similar coated members, as well as processes for the production thereof. The present invention provides a wide range of benefits not previously available in the art, including cost savings, space savings, lessened environmental impact, improved physical and operational properties, continuous process operation, and the like.
In particular, the present invention, in embodiments, provides a process for making a multiple-layer elastomer-coated member, comprising:
applying a coating of an elastomeric material to a supporting substrate; and
curing the elastomeric material by exposure to radiant energy in a radiant energy curing apparatus.
The present invention also provides members, such as fuser or fixing members, made by such a process.